Data Layer: Dynamic Styling

This example uses a data layer to dynamically change the appearance of some KML feature objects when the user hovers over or clicks them.

Read the documentation.

TypeScript

let map: google.maps.Map;

function initMap(): void {
  map = new google.maps.Map(document.getElementById("map") as HTMLElement, {
    zoom: 4,
    center: { lat: -28, lng: 137 },
  });

  // Load GeoJSON.
  map.data.loadGeoJson(
    "https://storage.googleapis.com/mapsdevsite/json/google.json"
  );

  // Color each letter gray. Change the color when the isColorful property
  // is set to true.
  map.data.setStyle((feature) => {
    let color = "gray";

    if (feature.getProperty("isColorful")) {
      color = feature.getProperty("color");
    }
    return /** @type {!google.maps.Data.StyleOptions} */ {
      fillColor: color,
      strokeColor: color,
      strokeWeight: 2,
    };
  });

  // When the user clicks, set 'isColorful', changing the color of the letters.
  map.data.addListener("click", (event) => {
    event.feature.setProperty("isColorful", true);
  });

  // When the user hovers, tempt them to click by outlining the letters.
  // Call revertStyle() to remove all overrides. This will use the style rules
  // defined in the function passed to setStyle()
  map.data.addListener("mouseover", (event) => {
    map.data.revertStyle();
    map.data.overrideStyle(event.feature, { strokeWeight: 8 });
  });

  map.data.addListener("mouseout", (event) => {
    map.data.revertStyle();
  });
}index.ts

JavaScript

let map;

function initMap() {
  map = new google.maps.Map(document.getElementById("map"), {
    zoom: 4,
    center: { lat: -28, lng: 137 },
  });
  // Load GeoJSON.
  map.data.loadGeoJson(
    "https://storage.googleapis.com/mapsdevsite/json/google.json"
  );
  // Color each letter gray. Change the color when the isColorful property
  // is set to true.
  map.data.setStyle((feature) => {
    let color = "gray";

    if (feature.getProperty("isColorful")) {
      color = feature.getProperty("color");
    }
    return /** @type {!google.maps.Data.StyleOptions} */ {
      fillColor: color,
      strokeColor: color,
      strokeWeight: 2,
    };
  });
  // When the user clicks, set 'isColorful', changing the color of the letters.
  map.data.addListener("click", (event) => {
    event.feature.setProperty("isColorful", true);
  });
  // When the user hovers, tempt them to click by outlining the letters.
  // Call revertStyle() to remove all overrides. This will use the style rules
  // defined in the function passed to setStyle()
  map.data.addListener("mouseover", (event) => {
    map.data.revertStyle();
    map.data.overrideStyle(event.feature, { strokeWeight: 8 });
  });
  map.data.addListener("mouseout", (event) => {
    map.data.revertStyle();
  });
}
index.js

CSS

/* Always set the map height explicitly to define the size of the div
       * element that contains the map. */
#map {
  height: 100%;
}

/* Optional: Makes the sample page fill the window. */
html,
body {
  height: 100%;
  margin: 0;
  padding: 0;
}
style.css

HTML

<!DOCTYPE html>
<html>
  <head>
    <title>Data Layer: Dynamic Styling</title>
    <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>
    <script
      src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&callback=initMap&libraries=&v=weekly"
      defer
    ></script>
    <link rel="stylesheet" type="text/css" href="./style.css" />
    <script src="./app.js"></script>
  </head>
  <body>
    <div id="map"></div>
  </body>
</html>sample.html

All

<!DOCTYPE html>
<html>
  <head>
    <title>Data Layer: Dynamic Styling</title>
    <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>
    <script
      src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&callback=initMap&libraries=&v=weekly"
      defer
    ></script>
    <style type="text/css">
      /* Always set the map height explicitly to define the size of the div
       * element that contains the map. */
      #map {
        height: 100%;
      }

      /* Optional: Makes the sample page fill the window. */
      html,
      body {
        height: 100%;
        margin: 0;
        padding: 0;
      }
    </style>
    <script>
      "use strict";

      let map;

      function initMap() {
        map = new google.maps.Map(document.getElementById("map"), {
          zoom: 4,
          center: {
            lat: -28,
            lng: 137,
          },
        }); // Load GeoJSON.

        map.data.loadGeoJson(
          "https://storage.googleapis.com/mapsdevsite/json/google.json"
        ); // Color each letter gray. Change the color when the isColorful property
        // is set to true.

        map.data.setStyle((feature) => {
          let color = "gray";

          if (feature.getProperty("isColorful")) {
            color = feature.getProperty("color");
          }

          return (
            /** @type {!google.maps.Data.StyleOptions} */
            {
              fillColor: color,
              strokeColor: color,
              strokeWeight: 2,
            }
          );
        }); // When the user clicks, set 'isColorful', changing the color of the letters.

        map.data.addListener("click", (event) => {
          event.feature.setProperty("isColorful", true);
        }); // When the user hovers, tempt them to click by outlining the letters.
        // Call revertStyle() to remove all overrides. This will use the style rules
        // defined in the function passed to setStyle()

        map.data.addListener("mouseover", (event) => {
          map.data.revertStyle();
          map.data.overrideStyle(event.feature, {
            strokeWeight: 8,
          });
        });
        map.data.addListener("mouseout", (event) => {
          map.data.revertStyle();
        });
      }
    </script>
  </head>
  <body>
    <div id="map"></div>
  </body>
</html>
inline.html

"use strict"; let map; function initMap() { map = new google.maps.Map(document.getElementById("map"), { zoom: 4, center: { lat: -28, lng: 137, }, }); // Load GeoJSON. map.data.loadGeoJson( "https://storage.googleapis.com/mapsdevsite/json/google.json" ); // Color each letter gray. Change the color when the isColorful property // is set to true. map.data.setStyle((feature) => { let color = "gray"; if (feature.getProperty("isColorful")) { color = feature.getProperty("color"); } return ( /** @type {!google.maps.Data.StyleOptions} */ { fillColor: color, strokeColor: color, strokeWeight: 2, } ); }); // When the user clicks, set 'isColorful', changing the color of the letters. map.data.addListener("click", (event) => { event.feature.setProperty("isColorful", true); }); // When the user hovers, tempt them to click by outlining the letters. // Call revertStyle() to remove all overrides. This will use the style rules // defined in the function passed to setStyle() map.data.addListener("mouseover", (event) => { map.data.revertStyle(); map.data.overrideStyle(event.feature, { strokeWeight: 8, }); }); map.data.addListener("mouseout", (event) => { map.data.revertStyle(); }); }

/* Always set the map height explicitly to define the size of the div * element that contains the map. */ #map { height: 100%; } /* Optional: Makes the sample page fill the window. */ html, body { height: 100%; margin: 0; padding: 0; }

<!DOCTYPE html> <html> <head> <title>Data Layer: Dynamic Styling</title> <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script> <script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyBIwzALxUPNbatRBj3Xi1Uhp0fFzwWNBkE&callback=initMap&libraries=&v=weekly" defer ></script>  </head> <body> <div id="map"></div> </body> </html>

Create a starter application from sample

A skeleton starter application using TypeScript, Webpack, and Babel can be generated from this sample using one of the methods below.

Run Locally

Node.js is required to run this sample locally. Follow these instructions to install Node.js and NPM.

npm i -g '@googlemaps/js-samples'
googlemaps-js-samples init layer-data-dynamic DESTINATION_FOLDER

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